Templates - Tags to change behavior

By default, when a template is transcluded (or substituted), the entire wikitext (code) of the template page gets included in that of the target page. However it is possible to modify that behavior, using tags that specify which parts of the template code are to be included. Here follow the main tags:

• <noinclude>...</noinclude> – the text between the noinclude tags will not be included when the template is transcluded (substituted), but will be processed on the template's page.
• <includeonly>...</includeonly> – the text between the includeonly tags will be transcluded (substituted), but will not be processed on the template's own page.
• <onlyinclude>...</onlyinclude> (not often used) – specifies that nothing on the page except what appears between the onlyinclude tags will be transcluded (substituted).

This help comes from: Help:Template page on Wikipedia